tembo · tembo · Aug 28, 2026
@@ -58,6 +58,8 @@
                                 "pages": [
                                     "features/sandbox/overview",
                                     "features/projects",
+                                    "features/sandbox/computer",
+                                    "features/sandbox/keep-alive",
                                     "features/sandbox/custom-dependencies",
                                     "features/sandbox/environment-variables"
                                 ]

@@ -0,0 +1,65 @@
+---
+title: 'Computer'
+description: 'Watch and control the sandbox desktop while a session runs.'
+---
+
+The **Computer** tab streams the Linux desktop running inside your session's [sandbox](/features/sandbox/overview) into the Tembo dashboard. Use it to watch what an agent is doing in a browser or editor, and to take over with your own mouse and keyboard when you want to drive the environment yourself.
+
+The desktop runs in the same VM as the agent, so both see the same `/workspace`, the same installed [dependencies](/features/sandbox/custom-dependencies), and the same [environment variables](/features/sandbox/environment-variables).
+
+## Prerequisites
+
+- The session runs in a VM sandbox.
+- The VM is running. If it has stopped, send a message in the session to start it again.
+
+## Open the Computer tab
+
+1. Open a session in the [dashboard](https://app.tembo.io).
+2. In the session's right sidebar, select **Computer**.
+
+The sidebar also holds **Changes**, **Artifacts**, **Files**, **Terminal**, and **VM logs**. In the expanded view these open as tabs, so you can keep the desktop next to a diff or a terminal.
+
+## What's on the desktop
+
+A dock at the bottom of the desktop launches the tools bundled into the sandbox image:
+
+| Dock item | Application | Opens |
+|-----------|-------------|-------|
+| Menu | Ulauncher | Application search |
+| Browser | Chromium | `about:blank` |
+| Files | PCManFM | `/workspace` |
+| Code | Visual Studio Code | `/workspace` |
+| Terminal | Ghostty | `/workspace` |
+
+Because agents drive this same desktop, browser automation and other GUI work show up live in the preview.
+
+## Copy and paste
+
+The stream carries the clipboard in both directions, so you can copy text out of the sandbox desktop and paste your own text into it using your normal keyboard shortcuts.
+
+## Copy or refresh the preview URL
+
+While the **Computer** tab is open, two buttons appear in the sidebar header:
+
+- **Copy computer URL** copies the preview URL so you can open the desktop in its own browser tab.
+- **Refresh computer URL** re-establishes the tunnel to the desktop. Use it if the stream looks stale or blank.
+
+<Note>
+  The preview URL changes whenever the tunnel restarts. A URL you copied earlier stops working after a refresh or after the VM restarts — copy it again.
+</Note>
+
+## Preview states
+
+| State | What it means |
+|-------|---------------|
+| **Computer is booting up** | The VM is still starting. The message names the current boot phase. |
+| **Refreshing computer URL** | A refresh is in flight. The preview reloads when the new URL is ready. |
+| **Computer unavailable** | The session has no running VM. The preview appears once a VM is running. |
+
+After the VM reports as running, the desktop stream can take up to about a minute to become available. Tembo keeps polling for it in the background and reloads the preview automatically.
+
+## Constraints
+
+- The desktop is streamed at 60 FPS from inside the sandbox. Throughput depends on your network connection to the tunnel.
+- Docker-based sandboxes do not run a desktop, so the **Computer** tab stays unavailable for them.
+- The desktop is part of the sandbox, so the stream ends when the VM stops. Extend the session's [keep-alive window](/features/sandbox/keep-alive) if you want the desktop to stay up after the agent finishes.
@@ -0,0 +1,79 @@
+---
+title: 'Keep Alive'
+description: 'Control how long a session sandbox keeps running after the agent finishes.'
+---
+
+A session's [sandbox](/features/sandbox/overview) VM does not stop the moment an agent finishes. Tembo holds it open for a short keep-alive window so you can read the diff, run commands in the terminal, or drive the [Computer](/features/sandbox/computer) desktop. When the window expires, Tembo stops the VM.
+
+Keep-alive is what you extend when you want more time in a live sandbox — and what to watch when a sandbox disappears sooner than you expected.
+
+## Default windows
+
+Each time work completes in a session, Tembo pushes the stop time out based on where the work came from:
+
+| Where the work came from | Keep-alive after it finishes |
+|--------------------------|------------------------------|
+| Dashboard session or chat message | 10 minutes |
+| Slack message or reply | 5 minutes |
+| Scheduled or triggered [agent](/features/agents) | 1 minute |
+
+These automatic extensions only ever move the stop time later. They never shorten a longer window you set yourself.
+
+<Note>
+  Self-hosted deployments can change the dashboard and Slack windows with the `SANDBOX_KEEP_ALIVE_APP_MINUTES` and `SANDBOX_KEEP_ALIVE_SLACK_MINUTES` environment variables. See [Self-hosted](/features/self-hosted/overview).
+</Note>
+
+## An open session tab holds the VM open
+
+While a session is the active tab and your browser window is focused, the dashboard sends a keep-alive heartbeat every 4 minutes that pushes the stop time 10 minutes out. You do not need to do anything to keep a sandbox alive while you are actively looking at it.
+
+Switching tabs, backgrounding the window, or closing the session stops the heartbeat, so the VM stops roughly 10 minutes later.
+
+## Extend from the composer
+
+To hold a sandbox open for longer than the default window:
+
+1. Type `/` in the session composer.
+2. Select **Keep alive**.
+3. Choose **10 minutes**, **1 day**, or **1 week**.
+
+A checkmark marks the window that is currently in effect. If the session has no running VM, the option reads **No active VM** and cannot be selected.
+
+<Warning>
+  Choosing a duration sets the window from now, so it can shorten an existing one. Selecting **10 minutes** while a 1 week window is active leaves 10 minutes, not a week and 10 minutes.
+</Warning>
+
+## Extend from inside the sandbox
+
+Run the `tembo` CLI from a session terminal, a [hook](/features/hooks), or a script:
+
+```bash
+tembo set-vm-keep-alive 3600
+```
+
+The argument is a positive whole number of seconds. The command prints the new window:
+
+```json
+{
+  "vmId": "3f8a1c52-9d4e-4b7a-8f21-6c0b5d2e7a94",
+  "seconds": 3600,
+  "keepAliveUntil": "2026-01-01T12:00:00.000Z"
+}
+```
+
+The command fails if the session has no VM or if its VM is no longer running.
+
+Agents running in a session can do the same thing through Tembo's own MCP server, which exposes a `setVmKeepAlive` tool taking the same `seconds` argument. That is what an agent reaches for when you ask it to keep the sandbox up while you take a look.
+
+## When the window expires
+
+Tembo does not discard the sandbox outright. It suspends the VM, captures a session snapshot, then stops it. When the session needs a VM again — for example because you send another message — Tembo resumes from that snapshot instead of cloning and installing from scratch, falling back to the [project](/features/projects) environment and then to a cold boot if the snapshot cannot be restored.
+
+Tembo also skips stopping a VM that still has active agent work, even if the window has technically expired.
+
+## Constraints
+
+- Keep-alive applies to VM sandboxes and requires the VM to be running.
+- A VM that stays alive keeps consuming compute for the whole window, billed at the hourly rate for its [sandbox size](/resources/pricing#cloud-vm-compute-rates). A 1 week keep-alive on a large sandbox is expensive — prefer the shortest window that covers what you need.
+- Only one window is in effect at a time. Setting a new one replaces the previous value rather than adding to it.
+- The keep-alive window controls how long the VM stays up, not how long the session lasts. Sessions and their history remain available after the sandbox stops.
@@ -5,6 +5,8 @@ description: 'Secure, isolated environments where coding agents execute sessions
 
 Every session runs in its own isolated sandbox. Sandboxes are ephemeral: spun up for the session, destroyed when it's done. No code or state persists after execution.
 
+While a sandbox is running you can watch and control its desktop from the [Computer](/features/sandbox/computer) tab, and use [keep alive](/features/sandbox/keep-alive) to hold it open after the agent finishes.
+
 ## Data handling
 
 Your repository is cloned into the sandbox for the duration of a session and torn down when the session ends — no repository contents or working state persist afterward.
@@ -15,7 +17,7 @@ Model providers handle prompt data according to their own retention policies —
 
 ## Sandbox sizes
 
-Tembo offers five sandbox sizes. Each session runs in a dedicated Linux VM, and no two sessions share the same VM.
+Each session runs in a dedicated Linux VM, and no two sessions share the same VM.
 
 | Size | vCPU | Memory | Disk |
 |------|------|--------|------|
@@ -24,10 +26,12 @@ Tembo offers five sandbox sizes. Each session runs in a dedicated Linux VM, and
 | Medium | 4 | 8 GB | 50 GB |
 | Large | 8 | 16 GB | 100 GB |
 | XL | 16 | 32 GB | 200 GB |
+| XXL | 16 | 64 GB | 200 GB |
+| Ultra | 32 | 128 GB | 200 GB |
 
 Micro and Medium are best for routine code analysis, fixes, features, and reviews. Large and XL are best for heavier builds, integration tests, Docker workloads, large repositories, or multi-container setups.
 
-Need more than 32 GB of RAM? Contact [support@tembo.io](mailto:support@tembo.io) to request access.
+Your plan sets the largest size you can select — see [Plans](/resources/pricing#plans). XXL and Ultra are not included in a standard plan; contact [support@tembo.io](mailto:support@tembo.io) to request access.
 
 VM sandboxes include full nested virtualization for Docker-in-Docker and provide a stronger isolation boundary.